Preparation and Fertilizer Efficiency study of magnetic micro-nano solid biogas fertilizer
In order to realize the absorption,recovery and utilization of nutrients in biogas slurry,the magnetic micro-nano biochar zeolite composite materials were prepared by solvothermal method in this study.The nutrient release characteristics of the composite materials recovered after adsorption of biogas slurry were then investigated through nutrient extraction test.Pot experiments were carried out to study the impacts on the growth of lettuce and the physical and chemical properties of soil.The results showed that,the synthesized magnetic micro-nano biochar zeolite composite had a specific surface area of 187.6 m2/g,and the average particle size in water was 1.48 μm.The loaded iron oxide was present as nanoscale Fe3O4 with a grain size of around 9.5 nm.The saturation magnetization strength of the com-posite material was 13.4 emu/g,which could be separated and recovered from water through an external magnetic field.After 30 days of leaching test,the nutrient accumulation dissolution rate of the solid bio-gas fertilizer was 71.97％,which had better nutrient slow-release performance compared to ordinary fer-tilizers.The pot experiment result showed that when compared with the non-fertilized control,the treat-ments with solid biogas fertilizers which replacing nitrogen fertilizer in different proportions,could signifi-cantly increase the biomass and chlorophyll content of lettuce,and increase soil pH by 0.13-0.44 units,organic matter content by 3.0％-20.0％,total nitrogen and total phosphorus content by 17.8％-27.1％and 26.5％-45.5％,respectively,and effective nitrogen and phosphorus content by 22.0％-49.8％.In comparison to applying fertilizer and biogas slurry treatment,the treatment which replacing 40％of the nitrogen fertilizer by solid biogas fertilizer was superior.Therefore,the magnetic micro-nano biochar zeolite composite prepared in this study could be used for nutrient adsorption and recovery in bio-gas slurry,and the obtained solid biogas fertilizer presents good nutrient release performance and high fer-tilizer efficiency value.
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